The present invention relates to a color filter unit, and more particularly to a filter drive unit for selectively positioning one of color filter members to a position in an exposure device.
In one type of an exposure device, a monochromatic CRT is used for displaying a monochromatic image and one of red, green and blue filter members is selectively positioned between the CRT screen and a photosensitive surface of a photosensitive sheet. The CRT serves as a light source as well as an original image source, which image is focussed on the photosensitive surface for exposure through the selected one of the filter members.
According to a conventional filter unit, a circular filter plate is divided into three sections at equi-angular arrangement such as by every 120 degrees so as to provide three color filters on the circular plate. If the CRT displays an image indicative of red color data on its CRT screen, a red filter is rotationally positioned between the CRT screen and the photosensitive surface of the photosensitive sheet. The same is true with respect to images indicative of green and blue color data. Further, in case of the white color data, no filter is positioned in front of the CRT screen.
According to another type of a conventional filter unit, these color filters are arranged in a linear array, and one of the color filters is selectively positioned at an optical path by linear motion of the filter unit.
The filter unit is generally assembled at a narrow space, and there has been a spacial problems for assembling the filter unit in such a narrow space of the exposure de vice, and in extreme cases, the filter unit cannot be installed in the exposure device due to spacial problems. Further, if one of the filters is intended to be replaced by remaining one of the filters, the one filter is moved, and then the intended filter is brought to the given position at the optical path. Therefore, filter switching requires relatively prolonged period.
Incidentally a co-pending U.S. Pat. application Ser. No. 260,034 filed on Oct. 20, 1988 discloses color control filter unit movably disposed at a light path.